Rear lamps for bicycles as well as for any other vehicles have to be designed to provide a good visibility for other motorists and cyclists. For a maximum safety the rear lamp needs to be seen from the back as well as from the side. Commonly known bike rear lamps often use stray light to ensure side visibility which is typically week, or they use additional LEDs just for the side visibility which then do not contribute the back visibility resulting in an extremely inefficient operation.
DE 20 2010 003 752 U1 discloses a LED rear lamp for a bicycle providing a good visibility from the back as well as from the side. The disclosed rear lamp comprises a light guide having a flat main portion passing over in curved side portions. The LED is arranged centrally behind the main portion of the light guide such that a main emission direction of the LED is aligned towards the opposing main surface of the main portion. The light guide is designed to internally reflect the light of the LED towards the side portions. A first portion of this light is then a second time internally reflected to escape through the main surface of the main portion. The second portion through the main surface of the curved side portions. Due to the design of this curved side portions the side visibility is achieved.